whats up fellas im having a misfire on my evo 8, i did get a CEL for my cat (p0420) but i have no cats it sputters/pops under load, starts right around 3,500 RPM i changed my plugs and the car ran fine. The next day it started to do it again i got another CEL but for the same code. any ideas?

 

Is the car tuned? What mods does it have?

 

the car is not tuned due to the fact that its all stock, only mods are the K&N drop in and a HKS turbo back

 

Got ya. Well it's breaking up starting at about 3.5 new plugs helped for a little then issue returned.

Was the car tuned prior to you getting it? I would def say to find somewhere/someone in your area that can log the car. This could give you a little more insight into whats going on.

Could be fuel, ignition, and/or airflow related.

 

You using the right plugs? Also check your MAF.

 

i think so, the gap is set at .39 stock spec was like .40 i think..

 

Word, thank you every much for your help i'm gunna keep looking for the issue

 

mine is doing the same thing. I just put brand new spark plugs in too. as soon as i go wot it hesitates and sounds like it has multiple misfires. i did a boost leak check and only leak was the throttle body seals. i just cleaned the maf. Ill let you know if that fixed the problem. i would check your gap on the plugs.... .22 to.25 is what i was told to gap them at

 

also try using someone else coil packs... yours could be going bad

 

thanks brotha! ill give that a shot i just orded some NGK plugs

yea i tried that still same thing i even think it got worse.

 

Wow, mine is set at .22 it might not hurt to try a smaller gap. Good thing is it doesn't take long to try it.

 

yea im gunna give that a shot but even with the gap at .39 it went away but came back the next day. took the car out to auto zone today and on the way back i got an other CEL i checked it out when i got home and its the same code for the cat (P0420)

 

Maybe you have a bad connection with one of the plug wires? I would try disconnecting 1 wire at a time... if you disconnect one and it doesnt change at all, then I would say that is the wire/cylinder that is having issues? If all of them make it worse when unplugged you can rule out the plugs and wires.

 

yes sir did that, number two was weak as to all the others had decent spark changed the coil and still the same thing

 

The factory gap on an EVO 8 is .028-.031. But I would recommend .025-.028